/*******************************************************************************
 * Copyright (c) 2011 IBM Corporation and others. All rights reserved. This program and the
 * accompanying materials are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html Contributors: IBM Corporation - initial API and
 * implementation
 *******************************************************************************/
package org.eclipse.wst.sse.ui.internal.filter;

import java.util.Vector;

/**
 * A string pattern matcher. Supports '*' and '?' wildcards.
 */
public class StringMatcher {
  protected String fPattern;
  protected int fLength; // pattern length
  protected boolean fIgnoreWildCards;
  protected boolean fIgnoreCase;
  protected boolean fHasLeadingStar;
  protected boolean fHasTrailingStar;
  protected String fSegments[]; //the given pattern is split into * separated segments

  /* boundary value beyond which we don't need to search in the text */
  protected int fBound = 0;

  protected static final char fSingleWildCard = '\u0000';

  public static class Position {
    int start; //inclusive
    int end; //exclusive

    public Position(int start, int end) {
      this.start = start;
      this.end = end;
    }

    public int getStart() {
      return start;
    }

    public int getEnd() {
      return end;
    }
  }

  /**
   * StringMatcher constructor takes in a String object that is a simple pattern. The pattern may
   * contain '*' for 0 and many characters and '?' for exactly one character. Literal '*' and '?'
   * characters must be escaped in the pattern e.g., "\*" means literal "*", etc. Escaping any other
   * character (including the escape character itself), just results in that character in the
   * pattern. e.g., "\a" means "a" and "\\" means "\" If invoking the StringMatcher with string
   * literals in Java, don't forget escape characters are represented by "\\".
   * 
   * @param pattern the pattern to match text against
   * @param ignoreCase if true, case is ignored
   * @param ignoreWildCards if true, wild cards and their escape sequences are ignored (everything
   *          is taken literally).
   */
  public StringMatcher(String pattern, boolean ignoreCase, boolean ignoreWildCards) {
    if (pattern == null)
      throw new IllegalArgumentException();
    fIgnoreCase = ignoreCase;
    fIgnoreWildCards = ignoreWildCards;
    fPattern = pattern;
    fLength = pattern.length();

    if (fIgnoreWildCards) {
      parseNoWildCards();
    } else {
      parseWildCards();
    }
  }

  /**
   * Find the first occurrence of the pattern between <code>start</code)(inclusive) and
   * <code>end</code>(exclusive).
   * 
   * @param text the String object to search in
   * @param start the starting index of the search range, inclusive
   * @param end the ending index of the search range, exclusive
   * @return an <code>StringMatcher.Position</code> object that keeps the starting (inclusive) and
   *         ending positions (exclusive) of the first occurrence of the pattern in the specified
   *         range of the text; return null if not found or subtext is empty (start==end). A pair of
   *         zeros is returned if pattern is empty string Note that for pattern like "*abc*" with
   *         leading and trailing stars, position of "abc" is returned. For a pattern like"*??*" in
   *         text "abcdf", (1,3) is returned
   */
  public StringMatcher.Position find(String text, int start, int end) {
    if (text == null)
      throw new IllegalArgumentException();

    int tlen = text.length();
    if (start < 0)
      start = 0;
    if (end > tlen)
      end = tlen;
    if (end < 0 || start >= end)
      return null;
    if (fLength == 0)
      return new Position(start, start);
    if (fIgnoreWildCards) {
      int x = posIn(text, start, end);
      if (x < 0)
        return null;
      return new Position(x, x + fLength);
    }

    int segCount = fSegments.length;
    if (segCount == 0)//pattern contains only '*'(s)
      return new Position(start, end);

    int curPos = start;
    int matchStart = -1;
    int i;
    for (i = 0; i < segCount && curPos < end; ++i) {
      String current = fSegments[i];
      int nextMatch = regExpPosIn(text, curPos, end, current);
      if (nextMatch < 0)
        return null;
      if (i == 0)
        matchStart = nextMatch;
      curPos = nextMatch + current.length();
    }
    if (i < segCount)
      return null;
    return new Position(matchStart, curPos);
  }

  /**
   * match the given <code>text</code> with the pattern
   * 
   * @return true if matched eitherwise false
   * @param text a String object
   */
  public boolean match(String text) {
    return match(text, 0, text.length());
  }

  /**
   * Given the starting (inclusive) and the ending (exclusive) positions in the <code>text</code>,
   * determine if the given substring matches with aPattern
   * 
   * @return true if the specified portion of the text matches the pattern
   * @param text a String object that contains the substring to match
   * @param start marks the starting position (inclusive) of the substring
   * @param end marks the ending index (exclusive) of the substring
   */
  public boolean match(String text, int start, int end) {
    if (null == text)
      throw new IllegalArgumentException();

    if (start > end)
      return false;

    if (fIgnoreWildCards)
      return (end - start == fLength)
          && fPattern.regionMatches(fIgnoreCase, 0, text, start, fLength);
    int segCount = fSegments.length;
    if (segCount == 0 && (fHasLeadingStar || fHasTrailingStar)) // pattern contains only '*'(s)
      return true;
    if (start == end)
      return fLength == 0;
    if (fLength == 0)
      return start == end;

    int tlen = text.length();
    if (start < 0)
      start = 0;
    if (end > tlen)
      end = tlen;

    int tCurPos = start;
    int bound = end - fBound;
    if (bound < 0)
      return false;
    int i = 0;
    String current = fSegments[i];
    int segLength = current.length();

    /* process first segment */
    if (!fHasLeadingStar) {
      if (!regExpRegionMatches(text, start, current, 0, segLength)) {
        return false;
      } else {
        ++i;
        tCurPos = tCurPos + segLength;
      }
    }
    if ((fSegments.length == 1) && (!fHasLeadingStar) && (!fHasTrailingStar)) {
      // only one segment to match, no wildcards specified
      return tCurPos == end;
    }
    /* process middle segments */
    while (i < segCount) {
      current = fSegments[i];
      int currentMatch;
      int k = current.indexOf(fSingleWildCard);
      if (k < 0) {
        currentMatch = textPosIn(text, tCurPos, end, current);
        if (currentMatch < 0)
          return false;
      } else {
        currentMatch = regExpPosIn(text, tCurPos, end, current);
        if (currentMatch < 0)
          return false;
      }
      tCurPos = currentMatch + current.length();
      i++;
    }

    /* process final segment */
    if (!fHasTrailingStar && tCurPos != end) {
      int clen = current.length();
      return regExpRegionMatches(text, end - clen, current, 0, clen);
    }
    return i == segCount;
  }

  /**
   * This method parses the given pattern into segments seperated by wildcard '*' characters. Since
   * wildcards are not being used in this case, the pattern consists of a single segment.
   */
  private void parseNoWildCards() {
    fSegments = new String[1];
    fSegments[0] = fPattern;
    fBound = fLength;
  }

  /**
   * Parses the given pattern into segments seperated by wildcard '*' characters.
   */
  private void parseWildCards() {
    if (fPattern.startsWith("*"))//$NON-NLS-1$
      fHasLeadingStar = true;
    if (fPattern.endsWith("*")) {//$NON-NLS-1$
      /* make sure it's not an escaped wildcard */
      if (fLength > 1 && fPattern.charAt(fLength - 2) != '\\') {
        fHasTrailingStar = true;
      }
    }

    Vector temp = new Vector();

    int pos = 0;
    StringBuffer buf = new StringBuffer();
    while (pos < fLength) {
      char c = fPattern.charAt(pos++);
      switch (c) {
        case '\\':
          if (pos >= fLength) {
            buf.append(c);
          } else {
            char next = fPattern.charAt(pos++);
            /* if it's an escape sequence */
            if (next == '*' || next == '?' || next == '\\') {
              buf.append(next);
            } else {
              /* not an escape sequence, just insert literally */
              buf.append(c);
              buf.append(next);
            }
          }
          break;
        case '*':
          if (buf.length() > 0) {
            /* new segment */
            temp.addElement(buf.toString());
            fBound += buf.length();
            buf.setLength(0);
          }
          break;
        case '?':
          /* append special character representing single match wildcard */
          buf.append(fSingleWildCard);
          break;
        default:
          buf.append(c);
      }
    }

    /* add last buffer to segment list */
    if (buf.length() > 0) {
      temp.addElement(buf.toString());
      fBound += buf.length();
    }

    fSegments = new String[temp.size()];
    temp.copyInto(fSegments);
  }

  /**
   * @param text a string which contains no wildcard
   * @param start the starting index in the text for search, inclusive
   * @param end the stopping point of search, exclusive
   * @return the starting index in the text of the pattern , or -1 if not found
   */
  protected int posIn(String text, int start, int end) {//no wild card in pattern
    int max = end - fLength;

    if (!fIgnoreCase) {
      int i = text.indexOf(fPattern, start);
      if (i == -1 || i > max)
        return -1;
      return i;
    }

    for (int i = start; i <= max; ++i) {
      if (text.regionMatches(true, i, fPattern, 0, fLength))
        return i;
    }

    return -1;
  }

  /**
   * @param text a simple regular expression that may only contain '?'(s)
   * @param start the starting index in the text for search, inclusive
   * @param end the stopping point of search, exclusive
   * @param p a simple regular expression that may contains '?'
   * @return the starting index in the text of the pattern , or -1 if not found
   */
  protected int regExpPosIn(String text, int start, int end, String p) {
    int plen = p.length();

    int max = end - plen;
    for (int i = start; i <= max; ++i) {
      if (regExpRegionMatches(text, i, p, 0, plen))
        return i;
    }
    return -1;
  }

  protected boolean regExpRegionMatches(String text, int tStart, String p, int pStart, int plen) {
    while (plen-- > 0) {
      char tchar = text.charAt(tStart++);
      char pchar = p.charAt(pStart++);

      /* process wild cards */
      if (!fIgnoreWildCards) {
        /* skip single wild cards */
        if (pchar == fSingleWildCard) {
          continue;
        }
      }
      if (pchar == tchar)
        continue;
      if (fIgnoreCase) {
        if (Character.toUpperCase(tchar) == Character.toUpperCase(pchar))
          continue;
        // comparing after converting to upper case doesn't handle all cases;
        // also compare after converting to lower case
        if (Character.toLowerCase(tchar) == Character.toLowerCase(pchar))
          continue;
      }
      return false;
    }
    return true;
  }

  /**
   * @param text the string to match
   * @param start the starting index in the text for search, inclusive
   * @param end the stopping point of search, exclusive
   * @param p a string that has no wildcard
   * @return the starting index in the text of the pattern , or -1 if not found
   */
  protected int textPosIn(String text, int start, int end, String p) {

    int plen = p.length();
    int max = end - plen;

    if (!fIgnoreCase) {
      int i = text.indexOf(p, start);
      if (i == -1 || i > max)
        return -1;
      return i;
    }

    for (int i = start; i <= max; ++i) {
      if (text.regionMatches(true, i, p, 0, plen))
        return i;
    }

    return -1;
  }
}
